Data discard signalling procedure in a wireless communication system

ABSTRACT

The invention provides a data discard signalling procedure in a wireless communication system. If data is discarded by the transmitter, the transmitter needs to notify the receiver of the discard. A shortened move receiving window super-field is used to request the receiver to move its reception window and optionally to indicate the set of discarded RLC SDUs, as a result of an RLC SDU discard in the sender. A move receiving window acknowledgement super-field acknowledges the reception of a MRW SUFI. If various criteria are met, the SDU discard with explicit signalling procedure can be efficiently terminated resulting in increased transmission throughput. Utilizing the data discard signalling procedure of the present invention, transmission throughput is increased and the transmission performance is improved.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a wireless communicationsprotocol. More specifically, the present invention discloses a datadiscard signalling procedure.

[0003] 2. Description of the Prior Art

[0004] In a wireless communication system, a protocol data unit (PDU),which contains a segment of a service data unit (SDU), may betransmitted and retransmitted for a maximum number of transmissionswithout positive acknowledgement from the peer receiver. To control thetransmission window of the sender, a state variable VT(A) is defined tobe the sequence number (SN) following the SN of the last in-sequenceacknowledged PDU. Alternatively, to control the reception window of thereceiver, a state variable VR(R) is defined to be the SN following theSN of the last in-sequence PDU received. Another state variable, VR(H),is defined to be the SN following the highest SN of any received PDU. Adata (SDU) may be transmitted and retransmitted within a predefinedduration of time. After a time out period or after the number oftransmissions has reached a maximum number, the SDU is deemedout-of-date and is discarded by the transmitter. For acknowledged mode(AM) transmission, the transmitter needs to signal the receiver of thediscard of the SDU so that the receiver can move its reception windowaccordingly. This signalling procedure is called an SDU discard withexplicit signalling procedure. Refer to FIG. 1 which illustrates theprocedure.

[0005] A move receiving window (MRW) super-field 120 is utilized torequest the receiver 110 to move its reception window and optionally toindicate the set of discarded Radio Link Control (RLC) SDUs, as a resultof an RLC SDU discard in the Sender 100. The receiver 110 responds withan acknowledge signal 130.

[0006] However, in certain situations, the SDU discard with explicitsignalling procedure will not be terminated. In these situations thereceiver 110 has moved its reception window to a position which isexactly what the sender 100 wanted to signal to the receiver 110. If theprocedure is not terminated when this criterion is fulfilled, the sender100 must retransmit MRW SUFI 120 when an MRW timer expires. This willwaste radio resources and slow down the transmission throughput.

[0007] Furthermore, if the number of transmissions of MRW SUFI 120reaches its maximum value when this criterion is fulfilled, the RLCentity will unnecessarily reset itself. This results in a degradation oftransmission performance.

[0008] Therefore, there is a need for a more efficient data discardsignalling procedure that improves transmission throughput andperformance.

SUMMARY OF THE INVENTION

[0009] To achieve these and other advantages and in order to overcomethe disadvantages of the conventional method in accordance with thepurpose of the invention as embodied and broadly described herein, thepresent invention provides a data discard signalling procedure whichefficiently improves transmission throughput and performance.

[0010] A move receiving window super-field (MRW SUFI) is used to requestthe receiver to move its reception window and optionally to indicate theset of discarded RLC SDUs, as a result of an RLC SDU discard in thesender.

[0011] A length field of 4 bits indicates the number of SN_MRW_(i)fields in the super-field of type MRW.

[0012] The values “0001” through “1111” indicate SN_MRW_(i) 1 through 15respectively. The value “0000” indicates that one SN_MRW_(i) field ispresent and that the RLC SDU to be discarded in the receiver extendsabove the configured transmission window in the Sender.

[0013] The SN_MRW_(i) fields are 12 bits each. When “Send MRW” isconfigured, an SN_MRW_(i) shall be used to indicate the end of eachdiscarded RLC SDU, i.e. the number of SN_MRW_(i) fields shall equal thenumber of RLC SDUs discarded by that MRW SUFI. When “Send MRW” is notconfigured, an SN_MRW_(i) field shall be used to indicate the end of thelast RLC SDU to be discarded in the Receiver and additional ones mayoptionally be used to indicate the end of other discarded RLC SDUs.

[0014] SN_MRW_(i) is the sequence number of the PDU that contains thelength indicator of the i:th RLC SDU to be discarded in the receiver(except for SN_MRW_(LENGTH) when N_(LENGTH)=0). The order of theSN_MRW_(i) shall be in the same sequential order as the RLC SDUs thatthey refer to.

[0015] Additionally, SN_MRW_(LENGTH) requests the receiver to discardall PDUs with a sequence number less than SN_MRW_(LENGTH), and to movethe reception window accordingly.

[0016] Furthermore, when N_(LENGTH) is greater than 0, the receiver hasto discard the first N_(LENGTH) length indicators and the correspondingdata octets in the PDU with sequence number SN_MRW_(LENGTH).

[0017] N_(LENGTH) is 4 bits and is used together with SN_MRW_(LENGTH) toindicate the end of the last RLC SDU to be discarded in the receiver.

[0018] N_(LENGTH) indicates which length indicator in the PDU withsequence number SN_MRW_(LENGTH) corresponds to the last RLC SDU to bediscarded in the receiver. N_(LENGTH) equal to 0 indicates that the lastRLC SDU ended in the PDU with sequence number SN_MRW_(LENGTH) minus 1and that the first data octet in the PDU with sequence numberSN_MRW_(LENGTH) is the first data octet to be reassembled next.

[0019] A move receiving window acknowledgement (MRW_ACK) super-fieldacknowledges the reception of an MRW SUFI. The N field is 4 bits and isset equal to the N_(LENGTH) field in the received MRW SUFI if the SN_ACKfield is equal to the SN_MRW_(LENGTH) field. Otherwise N shall be set to0.

[0020] With the aid of this field in combination with the SN_ACK field,it can be determined if the MRW_ACK corresponds to a previouslytransmitted MRW SUFI.

[0021] The SN_ACK field is 12 bits and indicates the updated value ofVR(R) after the reception of the MRW SUFI. With the aid of this field incombination with the N field, it can be determined if the MRW_ACKcorresponds to a previously transmitted MRW SUFI.

[0022] The acknowledgement super-field (ACK SUFI) consists of a typeidentifier field (ACK) and a sequence number (LSN).

[0023] The LSN field is 12 bits and acknowledges the reception of allPDUs with sequence number less than last sequence number (LSN) that arenot indicated to be erroneous in earlier parts of the STATUS PDU. Thismeans that if the LSN is set to a value greater than VR(R), allerroneous PDUs shall be included in the same STATUS PDU and if the LSNis set to VR(R), the erroneous PDUs can be split into several STATUSPDUs. At the sender or transmitter, if the value of the LSN is less thanor equal to the value of the first error indicated in the STATUS PDU,VT(A) will be updated according to the LSN. Otherwise VT(A) will beupdated according to the first error indicated in the STATUS PDU. VT(A)is only updated based on STATUS PDUs where ACK SUFI (or MRW_ACK SUFI) isincluded. The LSN shall not be set to a value greater than VR(H) or lessthan VR(R).

[0024] In situations where “Send MRW” is not configured, there is noneed to signal the last discarded RLC SDU to the receiver. AllSN_MRW_(i) fields indicating the end of the RLC SDUs to be discarded inthe receiver are optionally included in the MWR SUFI. OnlySN_MRW_(LENGTH), which indicates the receiver to discard all PDUs with asequence number less than SN_MRW_(LENGTH) and move the reception windowaccordingly, is mandatorily included in the MWR SUFI. The shortened MRWSUFI has more chance to be piggybacked in an AMD PDU so that anadditional STATUS PDU can be saved. The radio performance is thereforeincreased by this invention.

[0025] The MRW SUFI can generally accommodate fifteen discarded SDUsbecause LENGTH field is four bit long and both LENGTH=0000 andLENGTH=0001 cases indicate one discarded SDU. However, there are casesthat fifteen discarded SDUs need be signalled in two separate SDUdiscard with explicit signalling procedures when “Send MRW” isconfigured. On the other hand, for the case that “Send MRW” is notconfigured, if there are more than 15 SDUs to be discarded, a single MRWSUFI, i.e. a single SDU discard with explicit signalling procedure isenough to signal the receiver to move its reception window.

[0026] The sender terminates the SDU discard with explicit signallingprocedure if various criteria are fulfilled. However, in certainsituations, the SDU discard with explicit signalling procedure will notbe terminated.

[0027] In certain cases the receiver has moved its reception window to aposition beginning from SN_MRW_(LENGTH), which is exactly what thetransmitter wanted to signal to the receiver. If the procedure is notterminated when this criterion is fulfilled, the transmitter mustretransmit MRW SUFI when Timer_MRW expires. This will waste radioresources and slow down the transmission throughput.

[0028] Furthermore, if the number of transmissions of MRW SUFI reachesits maximum value when this criterion is fulfilled, the RLC entity willunnecessarily reset itself. The transmission performance is degraded.

[0029] Therefore, the present invention provides a data discardsignalling procedure wherein the MWR SUFI is shortened for cases where“Send MRW” is not configured and the sender shall efficiently terminatethe SDU discard with explicit signalling procedure if certain criteriaare fulfilled.

[0030] Consequently, utilizing the data discard signalling procedure ofthe present invention, transmission throughput is increased and thetransmission performance is improved.

[0031] These and other objectives of the present invention will becomeobvious to those of ordinary skill in the art after reading thefollowing detailed description of preferred embodiments.

[0032] It is to be understood that both the foregoing generaldescription and the following detailed description are exemplary, andare intended to provide further explanation of the invention as claimed.

BRIEF DESCRITPION OF THE DRAWINGS

[0033] The accompanying drawings are included to provide a furtherunderstanding of the invention, and are incorporated in and constitute apart of this specification. The drawings illustrate embodiments of theinvention and, together with the description, serve to explain theprinciples of the invention. In the drawings,

[0034]FIG. 1 is a diagram showing an SDU discard with explicitsignalling procedure;

[0035]FIG. 2 is a drawing illustrating a format for a move receivingwindow super-field (MRW SUFI) according to an embodiment of the presentinvention;

[0036]FIG. 3 is a drawing illustrating a format of an MRW_ACK accordingto an embodiment of the present invention;

[0037]FIG. 4 is a drawing illustrating the ACK super-field in a STATUSPDU according to an embodiment of the present invention; and

[0038]FIG. 5 is a drawing illustrating PDU structure according to anembodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0039] Reference will now be made in detail to the preferred embodimentsof the present invention, examples of which are illustrated in theaccompanying drawings. Wherever possible, the same reference numbers areused in the drawings and the description to refer to the same or likeparts.

[0040] A move receiving window super-field is used to request thereceiver to move its reception window and optionally to indicate the setof discarded RLC SDUs, as a result of an RLC SDU discard in the sender.Refer to FIG. 2 which illustrates a format for the move receiving windowsuper-field (MRW SUFI).

[0041] In an embodiment of the present invention, the length field 220is 4 bits. It indicates the number of SN_MRW_(i) fields 230 in thesuper-field of type MRW 200.

[0042] The values “0001” through “1111” indicate that the number ofSN_MRW_(i) fields contained in the MRW SUFI is 1 through 15respectively. The value “0000” indicates that one SN_MRW_(i) field 230is present and that the RLC SDU to be discarded in the receiver extendsabove the configured transmission window in the sender.

[0043] The SN_MRW_(i) fields 230 are 12 bits each. When “Send MRW” isconfigured, an SN_MRW_(i) 230 shall be used to indicate the end of eachdiscarded RLC SDU, i.e. the number of SN_MRW_(i) fields 230 shall equalthe number of RLC SDUs discarded by that MRW SUFI. When “Send MRW” isnot configured, an SN_MRW_(i) field 230 shall be used to indicate theend of the last RLC SDU to be discarded in the receiver and additionalones may optionally be used to indicate the end of other discarded RLCSDUs.

[0044] SN_MRW_(i) is the sequence number of the PDU that contains thelength indicator of the i:th RLC SDU to be discarded in the receiver(except for SN_MRW_(LENGTH) 240 when N_(LENGTH)=0). The order of theSN_MRW_(i) shall be in the same sequential order as the RLC SDUs thatthey refer to.

[0045] Additionally SN_MRW_(LENGTH) 240 requests the receiver to discardall PDUs with a sequence number less than SN_MRW_(LENGTH) 240, and tomove the reception window accordingly.

[0046] Furthermore, when N_(LENGTH) 250 is greater than 0, the receiverhas to discard the first N_(LENGTH) length indicators and thecorresponding data octets in the PDU with sequence numberSN_MRW_(LENGTH) 240.

[0047] N_(LENGTH) 250 is 4 bits and is used together withSN_MRW_(LENGTH) 240 to indicate the end of the last RLC SDU to bediscarded in the receiver.

[0048] N_(LENGTH) 250 indicates which length indicator in the PDU withsequence number SN_MRW_(LENGTH) 240 corresponds to the last RLC SDU tobe discarded in the receiver. N_(LENGTH) 250 equals 0 indicates that thelast RLC SDU ended in the PDU with sequence number SN_MRW_(LENGTH) 240minus 1 and that the first data octet in the PDU with sequence numberSN_MRW_(LENGTH) 240 is the first data octet to be reassembled next.

[0049] A move receiving window acknowledgement super-field acknowledgesthe reception of a MRW SUFI. Refer to FIG. 3 which illustrates theformat of the MRW_ACK 300.

[0050] The N field 320 is 4 bits and is set equal to the N_(LENGTH)field in the received MRW SUFI if the SN_ACK field is equal to theSN_MRW_(LENGTH) field. Otherwise N 320 shall be set to 0.

[0051] With the aid of this field in combination with the SN_ACK field330, it can be determined if the MRW_ACK 300 corresponds to a previouslytransmitted MRW SUFI.

[0052] The SN_ACK field 330 is 12 bits and indicates the updated valueof VR(R) after the reception of the MRW SUFI. With the aid of this fieldin combination with the N field 320, it can be determined if the MRW_ACK300 corresponds to a previously transmitted MRW SUFI.

[0053] The sender terminates the SDU discard with explicit signallingprocedure if one of the following criteria is fulfilled:

[0054] a STATUS PDU/piggybacked STATUS PDU containing an MRW_ACK SUFI isreceived, and the SN_ACK field in the received MRW_ACK SUFI is greaterthan the SN_MRW_(LENGTH) field in the transmitted MRW_SUFI, and the Nfield in the received MRW_ACK SUFI is set equal to “0000”;

[0055] a STATUS PDU/piggybacked STATUS PDU containing an MRW_ACK SUFI isreceived, and the SN_ACK field in the received MRW_ACK SUFI is equal tothe SN_MRW_(LENGTH) field in the transmitted MRW_SUFI, and the N fieldin the received MRW_ACK SUFI is set equal to the N_(LENGTH) field in thetransmitted MRW SUFI;

[0056] a STATUS PDU/piggybacked STATUS PDU containing an ACK SUFI isreceived, and the LSN field in the received ACK SUFI is greater than theSN_MRW_(LENGTH) field in the transmitted MRW SUFI.

[0057] Refer to FIG. 4 which illustrates the ACK fields in a STATUS PDU.The acknowledgement super-field (ACK SUFI) 400 consists of a typeidentifier field (ACK) 410 and a sequence number (LSN) 420.

[0058] The LSN field 420 is 12 bits and acknowledges the reception ofall PDUs with sequence number less than LSN and not indicated to beerroneous in earlier parts of the STATUS PDU. This means that if the LSN420 is set to a value greater than VR(R), all erroneous PDUs shall beincluded in the same STATUS PDU and if the LSN 420 is set to VR(R), theerroneous PDUs can be split into several STATUS PDUs. At the sender ortransmitter, if the value of the LSN 420 is less than or equal to thevalue of the first error indicated in the STATUS PDU, VT(A) will beupdated according to the LSN 420. Otherwise VT(A) will be updatedaccording to the first error indicated in the STATUS PDU. VT(A) is onlyupdated based on STATUS PDUs where ACK SUFI (or MRW_ACK SUFI) isincluded. The LSN 420 shall not be set to a value greater than VR(H) orless than VR(R).

[0059] The third terminating criterion shown above can also berecognized as:

[0060] a STATUS PDU/piggybacked STATUS PDU containing ACK SUFI isreceived, and this STATUS PDU/piggybacked STATUS PDU acknowledges allPDUs up to and including the PDU with sequence number equal to theSN_MRW_(LENGTH) field in the transmitted MRW SUFI.

[0061] The above criterion is equivalent to:

[0062] a STATUS PDU/piggybacked STATUS PDU containing ACK SUFI isreceived, VT(A) to be updated by this STATUS PDU/piggybacked STATUS PDUis greater than the SN_MRW_(LENGTH) field in the transmitted MRW SUFI.

[0063] Both of these criteria are equivalent to:

[0064] On the reception of a STATUS PDU which contains an ACK SUFIindicating VR(R) is greater than SN_MRW_(LENGTH)

[0065] Refer to FIG. 5, which is a drawing illustrating PDU structureaccording to an embodiment of the present invention

[0066] SDU1 is carried by PDUs of SN=0 500, SN=1 510, SN=2 520, and SN=3530. SDU2 is carried by PDUs of SN=4 540 and SN=5 550. Suppose that“Send MRW” is not configured for this RLC entity and SDU1 is discardedby the sender so that a SDU discard with explicit signalling procedureis initiated. The previous example illustrated “an SN_MRW_(i) field 230shall be used to indicate the end of the last RLC SDU to be discarded inthe receiver”. Thus, two SN_MRW_(i) fields will be needed: SN_MRW₁=3 (12bits) and SN_MRW₂=SN_MRW_(LENGTH)=4(12 bits), together with LENGTH=2(0010, 4 bits) and N₂=N_(LENGTH)=0000 and Type=MWR(4 bits). Thus, atleast a total of 36 bits is needed.

[0067] In fact, for the case where “Send MRW” is not configured, thereis no need to signal the last discarded RLC SDU to the receiver. Thus,SN_MRW₁=3 can be omitted in the MRW SUFI. Therefore, twelve bits can besaved. The shortened MRW SUFI has more chance to be piggybacked in anAMD PDU so that an additional STATUS PDU can be saved. The radioperformance is therefore increased by this invention. This is anotheradvantage of the present invention.

[0068] In general, at the sender, if “Send MRW” is not configured forthis RLC entity, all SN_MRW_(i) fields indicating the end of the RLCSDUs to be discarded in the receiver are optionally included in the MWRSUFI. Only SN_MRW_(LENGTH) indicating the receiver to discard all PDUswith a sequence number less than SN_MRW_(LENGTH), and to move thereception window accordingly are mandatorily included.

[0069] In addition, if SN_MRW_(LENGTH) is the only SN_MRW_(i) fieldincluded in the MRW SUFI:

[0070] LENGTH=0001 if SN_MRW_(LENGTH) is within the configuredtransmission window; or

[0071] LENGTH=0000 if SN_MRW_(LENGTH) is above the configuredtransmission window.

[0072] Refer to FIG. 5 again. If SDU1 carried on PDUs of SN=0 500through SN=3 530 is discarded, the contents of MWR SUFI will be 24 bitslong only: Type=MRW (4 bits), LENGTH=0001, SN_MWR₁=4 (12 bits), N₁=0000.Thus 12 bits fewer are needed.

[0073] The MRW SUFI 200 can generally accommodate fifteen discarded SDUsbecause LENGTH field 220 is four bit long and both LENGTH=0000 andLENGTH=0001 cases indicate one discarded SDU. However, there are casesthat fifteen discarded SDUs need be signalled in two separate SDUdiscard with explicit signalling procedures when “Send MRW” isconfigured. On the other hand, for the case that “Send MRW” is notconfigured, if there are more than 15 SDUs to be discarded, a single MRWSUFI, i.e. a single SDU discard with explicit signalling procedure isenough to signal the receiver to move its reception window.

[0074] For the case where “Send MRW” is configured, when the lastdiscarded SDU ended in an AMD PDU, and its Length Indicator is presentin the same AMD PDU, and no new SDU is present inside this AMD PDU,SN_MRW_(LENGTH) 240 must be set to equal to 1 plus the sequence numberof the PDU which contains the length indicator of the last discardedSDU. Only fourteen SN_MRW_(i) fields 230 are left to indicate the end ofeach discarded SDUs. Therefore, if the fifteenth discarded SDUs ended inan AMD PDU, and its Length Indicator is present in the same AMD PDU, andno new SDU is present inside this AMD PDU, this SDU can not be fitted inthe same MRW SUFI 200 as the other fourteen discarded SDUs and twoseparate SDU discard with explicit signalling procedures must beinitiated.

[0075] For the case where “Send MRW” is not configured, onlySN_MRW_(LENGTH) 240 is needed in spite of how many SDUs to be discarded.If there are more than fifteen SDUs to be discarded for this case, oneSDU discard with explicit signalling procedure is enough. No separateprocedures are needed. This will speed up the SDU discard procedure andimprove the radio transmission performance.

[0076] In addition, in certain situations, the SDU discard with explicitsignalling procedure will not be terminated. The following criterionwill not terminate the SDU discard with explicit signalling procedure:

[0077] a STATUS PDU/piggybacked STATUS PDU containing ACK SUFI isreceived, VT(A) to be updated by this STATUS PDU/piggybacked STATUS PDUis equal to the SN_MRW_(LENGTH) field in the transmitted MRW SUFI.

[0078] In fact, when the above criterion is fulfilled, the receiver hasmoved its reception window to a position beginning from SN_MRW_(LENGTH),which is exactly what the transmitter wanted to signal to the receiver.If the procedure is not terminated when this criterion is fulfilled, thetransmitter must retransmit MRW SUFI when Timer_MRW expires. This willwaste radio resources and slow down the transmission throughput.

[0079] Furthermore, if the number of transmissions of MRW SUFI reachesits maximum value when this criterion is fulfilled, the RLC entity willunnecessarily reset itself. The transmission performance is degraded.

[0080] Therefore, an embodiment of the present invention provides thatthe sender shall terminate the SDU discard with explicit signallingprocedure if the following criterion is fulfilled:

[0081] a STATUS PDU/piggybacked STATUS PDU containing ACK SUFI isreceived, VT(A) to be updated by this STATUS PDU/piggybacked STATUS PDUis greater than or equal to the SN_MRW_(LENGTH) field in the transmittedMRW SUFI.

[0082] In another embodiment of the present invention, the sender shallterminate the SDU discard with explicit signalling procedure if thefollowing criterion is fulfilled:

[0083] a STATUS PDU/piggybacked STATUS PDU containing ACK SUFI isreceived, and this STATUS PDU/piggybacked STATUS PDU acknowledges allPDUs up to and including the PDU with sequence number equal to theSN_MRW_(LENGTH) field in the transmitted MRW SUFI minus one.

[0084] In another embodiment of the present invention, the sender shallterminate the SDU discard with explicit signalling procedure if thefollowing criterion is fulfilled:

[0085] On the reception of a STATUS PDU which contains an ACK SUFIindicating VR(R) is greater than or equal to SN_MRW_(LENGTH)

[0086] If any of these various criteria are met, the SDU discard withexplicit signalling procedure can be efficiently terminated resulting inincreased transmission throughput. Utilizing the data discard signallingprocedure of the present invention, transmission throughput is increasedand the transmission performance is improved.

[0087] It will be apparent to those skilled in the art that variousmodifications and variations can be made to the present inventionwithout departing from the scope or spirit of the invention. In view ofthe foregoing, it is intended that the present invention covermodifications and variations of this invention provided they fall withinthe scope of the invention and its equivalent.

What is claimed is:
 1. A method for terminating a service data unit(SDU) discard with explicit signalling procedure comprising:transmitting a first status protocol data unit (STATUS PDU1) comprisinga move receiving window super-field (MRW SUFI) by a sender to areceiver; wherein the MRW SUFI comprises at least a sequence numberfield (SN_MRW_(LENGTH)); receiving a second status protocol data unit(STATUS PDU2) comprising an acknowledgement super-field (ACK SUFI) bythe sender from the receiver; wherein, if VT(A) to be updated by STATUSPDU2 is greater than or equal to SN_MRW_(LENGTH) in MRW SUFI, the SDUdiscard with explicit signalling procedure is terminated.
 2. The methodfor terminating the SDU discard with explicit signalling procedure ofclaim 1, wherein STATUS PDU1 is a piggybacked STATUS PDU.
 3. The methodfor terminating the SDU discard with explicit signalling procedure ofclaim 1, wherein STATUS PDU2 is a piggybacked STATUS PDU.
 4. A methodfor terminating the SDU discard with explicit signalling procedure ofclaim 1, wherein, if STATUS PDU2 acknowledges all protocol data units upto and including a protocol data unit with a sequence number equal toSN_MRW_(LENGTH) minus one, the SDU discard with explicit signallingprocedure is terminated.
 5. The method for terminating the SDU discardwith explicit signalling procedure of claim 4, wherein STATUS PDU1 is apiggybacked STATUS PDU.
 6. The method for terminating the SDU discardwith explicit signalling procedure of claim 4, wherein STATUS PDU2 is apiggybacked STATUS PDU.
 7. A method for terminating the SDU discard withexplicit signalling procedure of claim 1, wherein, if STATUS PDU2indicates a state variable VR(R) is greater than or equal toSN_MRW_(LENGTH), the SDU discard with explicit signalling procedure isterminated.
 8. The method for terminating the SDU discard with explicitsignalling procedure of claim 7, wherein STATUS PDU1 is a piggybackedSTATUS PDU.
 9. The method for terminating the SDU discard with explicitsignalling procedure of claim 7, wherein STATUS PDU2 is a piggybackedSTATUS PDU.
 10. A method for a service data unit (SDU) discard withexplicit signalling procedure comprising: discarding more than 15 SDUs;transmitting a first status protocol data unit (STATUS PDU1) comprisinga move receiving window super-field (MRW SUFI) by a sender to areceiver; wherein the MRW SUFI comprises at least a sequence numberfield (SN_MRW_(LENGTH)) indicating the receiver to discard all PDUs withsequence number < SN_MRW_(LENGTH) and to move a reception windowaccordingly.
 11. The method for the SDU discard with explicit signallingprocedure of claim 10, wherein the MRW SUFI comprises an N_(LENGTH)field indicating which length indicator in a PDU with sequence numberSN_MRW_(LENGTH) corresponds to a last RLC SDU to be discarded in thereceiver. 12 The method for the SDU discard with explicit signallingprocedure of claim 11, wherein N_(LENGTH) equals 0 indicates that a lastRLC SDU ended in the PDU with sequence number SN_MRW_(LENGTH) minus 1and that a first data octet in the PDU with sequence numberSN_MRW_(LENGTH) is a first data octet to be reassembled next.
 13. Themethod for the SDU discard with explicit signalling procedure of claim10, wherein STATUS PDU1 is a piggybacked STATUS PDU.
 14. A method forterminating a service data unit (SDU) discard with explicit signallingprocedure comprising: transmitting a first status protocol data unit(STATUS PDU1) comprising a move receiving window super-field (MRW SUFI)by a sender to a receiver; wherein the MRW SUFI comprises at least asequence number field (SN_MRW_(LENGTH)); receiving a second statusprotocol data unit (STATUS PDU2) comprising an acknowledgementsuper-field (ACK SUFI) by the sender from the receiver; wherein, ifVT(A) to be updated by STATUS PDU2 is greater than or equal toSN_MRW_(LENGTH) in MRW SUFI, the SDU discard with explicit signallingprocedure is terminated; wherein, if STATUS PDU2 acknowledges allprotocol data units up to and including a protocol data unit with asequence number equal to SN_MRW_(LENGTH) minus one, the SDU discard withexplicit signalling procedure is terminated; and wherein, if STATUS PDU2indicates a state variable VR(R) is greater than or equal toSN_MRW_(LENGTH), the SDU discard with explicit signalling procedure isterminated.
 15. The method for terminating the SDU discard with explicitsignalling procedure of claim 14, wherein STATUS PDU1 is a piggybackedSTATUS PDU.
 16. The method for terminating the SDU discard with explicitsignalling procedure of claim 14, wherein STATUS PDU2 is a piggybackedSTATUS PDU.
 17. A method for a service data unit (SDU) discard withexplicit signalling procedure comprising: discarding more than 15 SDUs;and transmitting a first status protocol data unit (STATUS PDU1)comprising a move receiving window super-field (MRW SUFI) by a sender toa receiver; wherein the MRW SUFI comprises an N_(LENGTH) fieldindicating which length indicator in a PDU with sequence numberSN_MRW_(LENGTH) corresponds to a last RLC SDU to be discarded in thereceiver; wherein the MRW SUFI comprises at least a sequence numberfield (SN_MRW_(LENGTH)) indicating the receiver to discard all PDUs withsequence number <SN_MRW_(LENGTH) and to move a reception windowaccordingly; and wherein N_(LENGTH) equals 0 indicates that a last RLCSDU ended in the PDU with sequence number SN_MRW_(LENGTH) minus 1 andthat a first data octet in the PDU with sequence number SN_MRW_(LENGTH)is a first data octet to be reassembled next.
 18. The method for the SDUdiscard with explicit signalling procedure of claim 17, wherein STATUSPDU1 is a piggybacked STATUS PDU.